U.S. patent number 6,924,956 [Application Number 10/140,302] was granted by the patent office on 2005-08-02 for head loading/unloading control system for use in disk drive apparatus.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Hiroshi Kurihara.
United States Patent |
6,924,956 |
Kurihara |
August 2, 2005 |
Head loading/unloading control system for use in disk drive
apparatus
Abstract
A method for controlling head loading/unloading operations in a
magnetic disk drive apparatus that can perform a head retracting
operation by using a reserve power source in order to retract head
elements to a predetermined rest position even when a primary power
source has shut down during the operation of the apparatus has been
developed. In order to guarantee proper power off unloading of head
elements at a shutdown time of the primary power source, a system
within the magnetic disk apparatus judges, prior to start the head
loading control, whether a sufficient electric power is secured in
a reserve system in order to retract the head elements to a
predetermined rest position if a shutdown of the power source
occurs.
Inventors: |
Kurihara; Hiroshi (Tokyo,
JP) |
Assignee: |
Kabushiki Kaisha Toshiba
(Tokyo, JP)
|
Family
ID: |
18984214 |
Appl.
No.: |
10/140,302 |
Filed: |
May 8, 2002 |
Foreign Application Priority Data
|
|
|
|
|
May 8, 2001 [JP] |
|
|
2001-137052 |
|
Current U.S.
Class: |
360/75; 360/69;
G9B/21.021; G9B/5.181 |
Current CPC
Class: |
G11B
5/54 (20130101); G11B 21/12 (20130101) |
Current International
Class: |
G11B
5/54 (20060101); G11B 21/12 (20060101); G11B
021/02 () |
Field of
Search: |
;360/69,75,78.01,78.04 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Tran; Sinh
Assistant Examiner: Olson; Jason
Attorney, Agent or Firm: Pillsbury Winthrop Shaw Pittman
LLP
Claims
What is claimed is:
1. A magnetic disk drive apparatus having head loading/unloading
functions and a head retracting function in order to retract head
elements to a predetermined rest position when a shutdown of a
primary power source occurs; the apparatus comprising: a reserve
power source configured to charge a power from the primary power
source during normal conditions and to discharge the power to
retract the head elements during a shutdown of the primary power
source; a detector configured to detect the power charged in the
reserve power source before starting a head loading operation; a
judging unit configured to judge whether the reserve power source
has charged a necessary power for retracting the head elements to
the rest position when a shutdown of the primary power source
occurs, based on the detected power; and a control unit configured
to allow the head loading operation only when it is judged that the
reserve power source has charged the necessary power.
2. The magnetic disk drive apparatus of claim 1, wherein: the
reserve power source includes a condenser configured to store
charges from the primary power source.
3. A magnetic disk drive apparatus for writing/reading data through
head elements to and from a recording medium, comprising: a spindle
motor configured to rotate the recording medium during data
reading/writing operations; a voice coil motor configured to move
the head element along a radius direction of the recording medium;
a head rest unit provided at a predetermined head rest position and
configured to retract the head element when the recording medium is
in a rotation stop state; a primary power source configured to
supply power voltage to the apparatus; a detector configured to
detect a shutdown of the primary power source; a controller
configured to move the head element to a target position on the
recording medium by controlling the voice coil motor during the
data reading/writing operations; and a reserve power source
configured to supply a power necessary for at least retracting the
head elements to the predetermined head rest position when the
detector detects a shutdown of the primary power source; wherein:
the controller is configured to retract the head element to the
predetermined head rest position by controlling the voice coil
motor when the detector detects the shutdown of the primary power
source; and wherein the controller is further configured to judge
whether the reserve power source holds a sufficient power voltage
necessary to retract the head element to the predetermined head
rest position before starting a loading control of the head element
and to start the loading control of the head element only when it
judges that the reserve power source holds a sufficient power
voltage.
4. The magnetic disk drive apparatus of claim 3, wherein: the
reserve power source includes a condenser configured to store
charges from the primary power source.
5. The magnetic disk drive apparatus of claim 3, wherein: the
controller further controls a power supplier configured to supply a
back electromotive force necessary to retract the head element to
the predetermined head rest position by using a back electromotive
voltage of the spindle motor when the detector detects the shutdown
of the primary power source.
6. The magnetic disk drive apparatus of claim 3, further including:
a first power source line configured to supply the primary power
source; a second power source line configured to supply the primary
power source supplied through the first power source line to the
controller; a third power source line configured to supply the
power source supplied through the second power source line to the
condenser; a fourth power source line configured to supply a power
charged in the condenser to the controller; and a switch unit
provided between the first and second power source lines; wherein:
the switch unit includes: a first switch element configured to
change from a closing state when the primary power source is being
supplied through the first power source line to an opening state
when the detector detects the shutdown of the power source; and a
second switch element provided between the second and third power
source lines so as to change from a closing state when the primary
power source is supplied through the first and second power source
lines to an opening state when the controller judges the voltage of
the reserve power source; and a third switch element provided
between the third and fourth power source lines configured to
switch to an open state only when the controller judges the voltage
of the reserve power source, wherein the controller judges whether
the condenser has charged the necessary voltage based on the power
supplied through the fourth power source line.
7. A method for controlling the head loading/unloading operation
applicable to a magnetic disk drive apparatus having a head
retracting function in order to retract head elements to a
predetermined rest position by using a reserve power source when a
shutdown of a primary power source occurs; the method including:
charging a power in the reserve power source from the primary power
source; detecting the power charged in the reserve power source;
judging whether the reserve power source has charged a necessary
power for retracting the head elements to the rest position when a
shutdown of the primary power source occurs; allowing head loading
operation only when it is judged that the reserve power source has
charged the necessary power.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority from Japanese
Patent Application No. 2001-137052, filed on May 8, 2001. This
application is hereby incorporated by reference in its
entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk drive apparatus having a
head loading/unloading control system and a method for controlling
head loading/unloading operations in the apparatus. More
particularly, it relates to an apparatus and a method for
performing reliable head loading/unloading operations even when a
shutdown of a primary power source occurs during the operation of
the disk drive apparatus.
2. Description of the Related Art
Conventionally, a magnetic disk drive apparatus, such as a hard
disk drive apparatus, (hereinafter simply referred to as a "disk
drive") is used for writing and/or reading data on and from a data
recording disk medium (hereinafter referred to as a "disk") by
loading magnetic head elements onto a target track in the disk when
the rotation speed of the disk reaches a steady state. A spindle
motor (SPM) rotates the disk. The head loading and/or unloading
operations are controlled by a central processing unit (CPU)
installed in the apparatus.
The writing/reading head elements are initially rested upon a rest
position. During the writing/reading operations, the head elements
are loaded from the rest position so as to float closely above a
surface of the disk when the rotation speed of the disk reaches a
steady state in order to avoid possible damage of data areas in the
disk due to contact between a head surface and a disk surface.
In order to prevent the head surface from contacting the rotating
disk surface during the head drive operations, usually, the disk
drive applies a contact-start-stop (CSS) system or a
loading/unloading system. In the CSS system, the head elements are
placed on a retract zone (CSS area) in the disk when the disk is in
a non-rotation state. Conventionally, the disk drive of the CSS
system includes a ring shaped CSS area at an inner side of the data
zone of the disk. In the disk drive of the head loading/unloading
system, the head elements are retracted (unloaded) onto a rest unit
(hereinafter, simply referred to as a "ramp unit") provided at near
the outer edge of the disk during when the disk is in a
non-rotation state. In both systems, the head elements are moved by
the rotation of a voice coil motor (VCM). A VCM drive circuit
supplies VCM drive currents in order to rotate the VCM.
In order to increase the data recording density of the disk, the
head surface is floated very closely to the disk surface. Thus, the
data recording density of the disk can be increased by reducing the
head floating height. However, the damages due to contact of the
head surface with the disk surface also increases when the head
floating power is reduced. Thus, if a shutdown of the primary power
source for the apparatus occurs during the operations of the disk
drive, the head surface will likely contact the disk surface due to
the inertia rotation of the spindle motor (SPM). In order to avoid
this defect in the disk drive, it needs to retract the head
elements to the CSS area or the ramp unit before stopping the
spindle motor (SPM). However, since the primary power source has
already shutdown, there is a need to supply the VCM drive current
in order to move the head elements to the rest position from a
reserve power source.
Conventionally, it has been proposed to perform a stabilized head
retracting operation at the time of a sudden shutdown of the
primary power source. For example, Japanese Patent Application No.
2000-21073 (the same assignee of this invention) has proposed to
acquire data for controlling the head retraction based on a head
position in a determination process during a normal operation of
the disk drive. Thus, in order to immediately perform the head
retracting operation at a shutdown time of the power source with a
lower electric power, the data for controlling a head retraction is
periodically acquired during a normal head driving control time.
When a shutdown of the primary power source occurs, the head
elements are moved to a retraction place by driving through an
auxiliary power supply. As the auxiliary power supply, a condenser
or the back electromotive voltages of the SPM are proposed.
The proposed head retracting operation by using the auxiliary power
supply, however, includes some defects. For example, if the primary
power source is shut down immediately after the disk drive is
operated, it is impossible to charge a sufficient battery voltage
in the condenser or to obtain a sufficient auxiliary power, by
rectifying the back electromotive force of the inertia rotation of
the SPM, for retracting the head elements.
Moreover, there is a possibility to have a failure of the condenser
even after a shutdown of the primary power source has occurred. If
the primary power source has shutdown in such a state, it is
impossible to retract the head elements to the rest position.
SUMMARY OF THE INVENTION
Therefore, there is a need for an apparatus and method to reliably
perform a head retracting operation to a predetermined rest
position when a shutdown of the primary power source occurs during
the operations of the disk drive. The disk drive apparatus and
methods according to the present invention solve the aforementioned
problems and defects of the conventional disk drive apparatus and
the head loading/unloading operations thereof. Namely, an object of
the present invention is to provide a disk drive and a method for
reliably performing head retracting operation when a shutdown of
the primary power source for the apparatus occurs.
In order to achieve the above-mentioned objects, according to the
present invention, there is provided a magnetic disk drive
apparatus having a judging mechanism for judging whether a
sufficient reserve power source for performing the head retracting
operation has already been secured even when a shutdown of a
primary power source occurs during the operations of the disk
drive, and only when it is judged that a sufficient reserve power
source has already been secured, a control of the head loading
operation is started.
A characteristic feature of the magnetic disk drive apparatus
consistent with the invention is to judge whether the disk drive
apparatus has a sufficient reserve power supply for performing the
head retracting operation to a rest position prior to starting the
head loading operation in the apparatus.
The magnetic disk drive apparatus consistent with the invention
includes: a detector for detecting a shutdown of a primary power
source; a controller for controlling the head movements onto a
target position in a recording medium by controlling the drive of a
voice coil motor, the controller retracting the head elements to a
rest position when the detector detects a shutdown of the primary
power source by controlling the drive of the voice coil motor; and
a reserve power source for supplying a necessary power for
retracting the head elements to the rest position when the detector
detects a shutdown of the primary power source; wherein, the
controller judges whether the reserve power source has charged the
necessary power for the head retracting operation prior to starting
the head loading control. Thus, the controller starts the head
loading control only when the controller has judged that the
reserve power source has charged a sufficient power for performing
the head retracting operation.
The magnetic disk drive apparatus consistent with the invention can
achieve a reliable head retracting operation even when a shutdown
of a primary power source occurs just after the disk drive
apparatus has started its operation, since the controller judges
whether the reserve power source has secured a necessary power for
performing the head retracting operation to a predetermined rest
position prior to starting the head loading control. Thus, the
magnetic disk drive apparatus consistent with the invention can
reliably perform the head loading/unloading operations in a primary
power-off time.
An embodiment consistent with the present invention relates to a
magnetic disk drive apparatus including a condenser for charging an
electric power as the reserve power source. Thus, the controller in
the embodiment consistent with the present invention judges whether
the condenser has charged a necessary power for performing a head
retracting operation at a time when a shutdown of the primary power
source occurs, prior to starting the head loading operation.
Another embodiment consistent with the present invention relates to
a magnetic disk drive apparatus including a condenser for charging
an electric power and a rectifying circuit for rectifying the
electromotive force of a spindle motor as the reserve power source.
Further, the magnetic disk drive apparatus includes a judging
mechanism for judging whether a sufficient reserve power has
obtained prior to starting the head loading operation in order to
perform the head retracting operation at a time when a shutdown of
the primary power source occurs.
The magnetic disk drive apparatus consistent with the present
invention includes head loading/unloading functions and a head
retracting function in order to retract head elements to a
predetermined rest position when a shutdown of a primary power
source occurs; the apparatus including: a reserve power source
configured to be charged from the primary power source; a detector
configured to detect the power charged in the reserve power source;
a judging unit configured to judge whether the reserve power source
has charged a necessary power for retracting the head elements to
the rest position when a shutdown of the primary power source
occurs; and a control unit configured to allow head loading
operation only when it is judged that the reserve power source has
charged the necessary power.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
part of this specification, illustrate various embodiments and/or
features of the invention and together with the description, serve
to explain the invention. Wherever possible, the same reference
numbers will be used throughout the drawings to the same or the
like parts. In the drawings:
FIG. 1 is a functional block diagram of an exemplary configuration
for magnetic disk drive apparatus in which methods and apparatus
consistent with the present invention may be implemented.
FIG. 2 depicts a partially enlarged view illustrating the main
components of the magnetic disk drive apparatus as depicted in FIG.
1 in order to explain the retracting operation of head elements to
a ramp unit.
FIG. 3 is a functional block diagram of an exemplary configuration
for a reserve power source for achieving a reliable head unloading
operation at a shutdown of the power source of the magnetic disk
drive apparatus in which methods and apparatus consistent with the
present invention may be implemented.
FIG. 4 is a flow chart for explaining operations for judging
control propriety of head loading in the configuration illustrated
in FIG. 3.
FIG. 5 is a flowchart for measuring a battery voltage of the
condenser illustrated in FIG. 3.
FIG. 6 illustrates a permissible voltage curve in order to explain
a method for judging normal/abnormal states of the condenser
illustrated in FIG. 3.
FIG. 7 is a functional block diagram for another exemplary
configuration for a reserve power source for achieving a reliable
head unloading operation at a shutdown of the power source of the
magnetic disk drive apparatus.
DETAILED DESCRIPTION
Reference will now be made in detail to the exemplary embodiments
of the invention, examples of which are illustrated in the
accompanying drawings. FIG. 1 illustrates the main components of a
magnetic disk drive apparatus 100 consistent with the invention.
The disk drive 100 includes a magnetic recording disk medium 10 of
which surfaces are coated with magnetic material, a spindle motor
(SPM) 20 for rotating the disk 10, and a rotary actuator 30 for
driving a head slider 40 along a radius direction of the disk 10.
The actuator 30 includes a suspension arm for holding the head
slider 40, and a voice coil motor (VCM) 50 for rotating the head
slider 40. The head slider 40 supports a pair of magnetic head
elements, i.e., a write head for writing data into the disk 10, and
a read head for reading data from the disk 10. Although only a
first head slider 40 is illustrated in order to simplify the
drawing, a practical disk drive apparatus includes a second head
slider facing a bottom surface if the disk 10 is for writing and
reading data. Furthermore, it is also possible to stack a plurality
of disks 10.
During operation of the disk drive apparatus 100, the SPM 20
rotates the disk 10 at a high-speed in a counterclockwise
direction. The read/write head elements supported on the head
slider 40 are floating close to a surface of the rotating disk 10.
Thus, the head slider 40 moves closely to a surface of the disk 10
along generally a radius direction of the disk 10 by rotation of
the rotary actuator 30. The rotary actuator 30 moves the heads and
determines a head position on a target track of the disks 10 under
a servo control. After seeking and positioning on a target track in
the disk 10, the head elements scan the track by the rotation of
the disk 10 in order to read servo patterns recorded in servo areas
on the track in the disk. A write head records data onto a target
data sector in the disk 10.
The disk drive 100 further includes a head amplifier circuit 2, a
read/write (R/W) circuit 3, a CPU 4, a primary power source
shutdown detecting circuit 5, a D/A converter 6, and a motor driver
7. Each of head elements on the head slider 40 is coupled to the
head amplifier circuit 2. Usually the head amplifier circuit 2 is
provided on a flexible printing circuit board (FPC). The head
amplifier circuit 2 amplifies analog output signals reproduced by
the read head from the disk 10. The head amplifier 2 further
includes a write amplifier for converting write data supplied from
the read/write circuit 3. The read/write (R/W) circuit 3 decodes
data from the reproduced signals. The R/W circuit 3 includes a
servo patterns reproducing circuit. Thus, the decoded data from the
reproduced signals includes servo patterns.
The R/W circuit 3 includes an automatic gain control (AGC) function
for amplifying the analog (read) signals supplied from the head
amplifier circuit 2 to a certain voltage and a decoding function
(read channel) for performing a signal processing necessary for
amplifying the read signals throught the AGC function, such as a
reproduction of NRZ code data. Further, the R/W circuit 3 has an
encoding function (write channel) for recording data into the disk
10 and a servo extraction function for extracting servo patterns
from the read signals.
The motor driver 7 includes a SPM driver 71 for driving the SPM 20
and a VCM driver 72 for driving the VCM 50. The SPM 20 is rotated
at a high speed by driving the control current supplied from the
SPM driver 71. Thus, the disk 10 is rotated at a high speed. The
VCM driver 72 supplies the control current to the VCM 50 in order
to drive the rotary actuator 30. In this embodiment, the motor
driver 7 is made as an integrated circuit of 1-chip. Each of the
control currents respectively supplied from the SMP driver 71 and
VCM driver 72 is determined by the CPU 4.
The CPU 4 is a main controller for the disk drive 100. The CPU 4
includes a read only memory (ROM) (not shown) for storing control
programs for performing various operations in the disk drive 100.
For example, a head control program performs head seeking and head
positioning based on the servo patterns extracted by the R/W
circuit 3. As illustrated in FIG. 1, CPU 4 includes a head control
circuit 41, a switch 44, and a serial interface (SI) 43. The bead
control circuit 41 provides control for driving the VCM driver 72
in order to drive the head elements onto a target position in the
disk 10 by calculating a distance between the target position and a
present head position. During a normal condition, the switch 44
connects between the output terminal 45 of the head control circuit
41 and the SI 43. Thus, the control amount calculated by the head
control circuit 41 is supplied to the VCM driver 72 through the
digital/analog D/A) converter 6.
Further, CPU 4 includes a power-off unloading control circuit 42.
When the primary power source shutdown detecting circuit 5 detects
an occurrence of a shutdown of the primary power source, the switch
44 is changed to connect between the output terminal 46 of the
power-off unloading control circuit 42 and the SI 44. The primary
power source shutdown detecting circuit 5 detects the shutdown by
monitoring a voltage level Vcc of the power source.
CPU 4 further includes a head unloading function for performing the
head retracting operation to the ramp block 60 when a shutdown of
the primary power source occurs. For the head unloading control at
a shutdown of the primary power source, the control amount
necessary for retracting the head elements from a presently loaded
position to the ramp block 60 is calculated based on a distance
between a retracting position and a presently loaded position.
Thus, CPU 4 includes a power-off unloading control circuit 42 and
the switch 44 for switching the outputs of the head control circuit
41 and the power-off unloading control circuit 42. Thus, when the
primary power source shutdown detecting circuit 5 detects a
shutdown of the primary power source, the switch circuit 44 is
connected to an output terminal 46 of the power-off unloading
control circuit 42.
The D/A converter 6 converts a digital control amount supplied
through the SI 43 in CPU 4 to an analog control amount in order to
supply to the VCM driver 72. When a shutdown of the primary power
source occurs, it needs to retract the head elements to the ramp
block 60 by supplying a reserve power source to a head unloading
control circuit system. Thus, the CPU 4, the D/A converter 6 and
the VCM driver 72 construct the head unloading control circuit
system. The detail structure of the reserve power source is
explained later.
A disk surface includes a predetermined number of reference servo
areas and a multiplicity of tracks. The reference servo patterns
include track address codes for detecting each of track position
and servo burst signals for detecting a head position in each of
tracks. In this embodiment shown in FIG. 1, the disk 10 includes an
unload head waiting area 110 at a middle portion between a most
outer data track and a most inner data track whereby the head
elements are held when any command is not given from the host
system for a certain time.
As illustrated in FIG. 2, when a shutdown of the primary power
source is detected, the head slider 40 is retracted onto the ramp
block 60. During the head unloading operation, an opposite drive
current to the head loading operation is supplied to the VCM 50. By
supplying the head unloading current to the VCM 50, the rotary
actuator 30 is moved to outside of the disk 10 so that the head
suspension arm 310 reaches the ramp block 60. The head suspension
arm 310 includes a top tab 311 for guiding and retracting the head
suspension arm 310 to the ramp block 60. The ramp block 60 is
provided on the rotation path of the top tab 311 and positioned
close to the outer edge of the disk medium 11.
The ramp block 60 includes a slanted portion 610 for guiding the
top tab 311 and sliding the head elements away from the surface of
the disk medium 10. The ramp block 60 includes a U-shaped groove
620 for holding a non-data area of the outer edge of the disk. When
the top tab 311 of the suspension arm 310 reaches the slanted
portion 610, the VCM driving force slides the top tab 311 upward
along the slanted portion 610 in order to separate the head
elements from the disk surface so that the head reaches a retract
position 630 on the ramp block 60.
FIG. 3 illustrates an embodiment of the reserve power source system
implemented in disk drive apparatus consistent with the invention.
As explained above, the reserve power source supplies a necessary
source voltage for performing the head unloading operation in order
to retract the head elements to a predetermined rest position when
a shutdown of the primary power source occurs. As illustrated in
FIG. 3, the reserve power source system includes CPU 4, primary
power source shutdown detecting circuit 5, D/A converter 6, VCM
driver 72, a condenser 9, and an A/D converter 8.
In this embodiment, the condenser 9 supplies a reserve source
voltage necessary for automatically retracting the head elements to
a predetermined rest position when a shutdown of the power source
is detected by the primary power source shutdown detecting circuit
5. Thus, the reserve power source for performing a power off
unloading operation is supplied from the condenser 9 only.
The primary power source shutdown detecting circuit 5 is connected
to the primary power source Vcc through a first power source line
91. The first power source line 91 is coupled to the VCM driver 72
through a first switch unit 81 and a second power source line 92.
The second power source line 92 transfers the source voltage Vcc to
the head unloading control circuit system that includes CPU 4, D/A
converter 6, and the VCM driver 72. The first switch unit 81 is
made of a semiconductor, such as, for example a field effect
transistor (FET). When the primary power source is supplied to the
disk drive 100, CPU 4 provides a first control signal 810 of a high
level so as to set the first switch unit 81 in a closed (ON) state.
Thus, when the primary power source supplies the source voltage
Vcc, the first switch unit 81 is closed (ON) in order to transfer
the source voltage Vcc to the VCM driver 72.
If a shutdown of the primary power source occurs, i.e., the primary
power source shutdown detecting circuit 5 detects an abnormal state
of the power source, the CPU 4 sets the first control signal 810 at
a low level in order to open (OFF) the first switch unit 81. Thus,
when a shutdown of the primary power source occurs, the first
switch unit 81 disconnects the second power source line 92 from the
first power source line 91.
CPU 4 is connected to the second power source line 92. CPU 4
further is coupled to the condenser 9 through a second switch unit
82 and a third power source line 93. Thus, the second switch unit
82 and the condenser 9 are sequentially provided between the second
power source line 92 and the grounding (GND). The second switch
unit 82 is also made of a semiconductor, such as, for example, a
FET. During a normal condition, the second switch unit 82 is closed
(ON) so as to charge the condenser 9 by the primary source voltage
Vcc.
When the primary power source shutdown detecting circuit 5 detects
a shutdown of the primary power source, the detecting signal is
supplied to CPU 4. Then, CPU 4 sets a second control signal 820 at
a low level in order to open (OFF) the second switch unit 82. Thus,
the reserve power charged in the condenser 9 is used for the head
unloading control circuit.
The third power source line 93 is coupled to a fourth power source
line 94 through a third switch unit 83. The fourth power source
line 94 is coupled to CPU 4 through the analog/digital (A/D)
converter 8. Further, the fourth power source line 94 is grounded
through a resister 12. The third switch unit 83 also is made of a
semiconductor, such as, for example a FET. During the normal
condition of the disk drive 100, the third switch unit 83 is opened
(OFF). When CPU 4 judges the battery voltage of the condenser 9,
CPU 4 sets a third control signal 830 at a high level in order to
close (ON) the third switch unit 83. Thus, the fourth power source
line 94 is used for supplying the battery voltage charged in the
condenser 9 to the A/D converter in order to measure the battery
voltage charged in the condenser 9.
During a normal condition, CPU 4 sets both the first and second
control signals 810 and 820 at a high level in order to close both
the first and second switch units 81 and 82. On the other hand,
when CPU 4 judges the reserve power voltage of the condenser 9, the
first and second control signals 810 and 820 are changed to a low
level in order to open the first and second switch units 81 and 82.
Further CPU 4 sets the third control signal 830 at a high level in
order to close the third switch unit 83.
When the second switch 82 is opened and the third switch 83 is
closed, the battery voltage charged in the condenser 9 is supplied
to CPU 4 through the A/D converter 8. The analog value of the
battery voltage of the condenser 9 is converted to a digital value
in order to supply to CPU 4. Based on the digital value of the
battery voltage supplied from the A/D converter 8, the CPU 4 judges
whether the battery voltage of the condenser 9 is in a normal state
or in an abnormal state.
FIG. 4 explains how CPU 4 judges as to the head loading propriety.
In the disk drive consistent with the invention, CPU 4 judges as to
the head loading propriety prior to CPU 4 actually starting the
head loading control. Either when the primary power source voltage
Vcc is supplied to the disk drive 100, or when a host system gives
an instruction to the SPM 71 for rotating the disk 10, in order to
load head elements from a retracted position onto the disk 10, CPU
4 starts a request for starting head loading control (step S1).
When the request is started, CPU 4 judges whether the number of
prohibition times of the head loading associated with the request
is not exceeded a predetermined number of times (loop) N (step S2).
If the prohibition times do not exceed the predetermined loop times
N (step S2, Yes), CPU 4 measures a battery voltage of the condenser
9 (step S3). Based on the measurement, the CPU 4 judges whether the
battery voltage of the condenser 9 is a normal state (step S4).
When CPU 4 judges that the battery voltage of the condenser 9 is a
normal state (step S4, Yes), CPU 4 allows the head loading
operation to start (step S5). Thus, only when CPU 4 judges that the
reserve power source has a sufficient power voltage for unloading
the head to the retract position is the head loading operation
allowed to start.
On the contrary, if the battery voltage of the condenser 9 is
judged as an abnormal state (step S4, No), CPU 4 temporarily
prohibits the start of the head loading operation (step S6). By
temporarily prohibiting the head loading operation, CPU 4 again
monitors the battery voltage of the condenser 9. Since a
predetermined processing time is needed for each measuring of the
battery voltage of the condenser 9, it may be possible to charge a
sufficient battery voltage in the condenser 9 through the primary
source voltage Vcc while CPU 4 repeats the measuring of the battery
voltage at several times, if the associated circuits keep its
normal conditions.
Even when CPU 4 has repeatedly monitored the battery voltage more
than the predetermined loop number of times N, if the battery
voltage of the condenser 9 still does not reach a normal value
(step S2, No), CPU 4 judges that some error occurs in the condenser
9 (step S7). Thus, CPU 4 does not start the head loading control,
but it sends a warning notice to a user through the host
system.
In order to judge whether the battery voltage of the condenser 9 is
a normal state or an abnormal state at the step S3 in FIG. 4, CPU 4
compares the measured battery voltage of the condenser 9 to a
predetermined set value. FIG. 5 explains the judging method. When a
measurement of the battery voltage of the condenser 9 is started
(step S21), CPU 4 provides instructions to change the second switch
element 82 to an OFF (open) state and also the third switch element
83 to an ON (closed) state (step S22). At the moment of the
switching when both switch elements 82 and 83 are changed, CPU 4
may obtain an initially measured voltage V0 of the condenser 9
through the A/D converter 8 (step S23). After a predetermined time
T1 has passed from changing the switches, CPU 4 again obtains a
second measured voltage V1 of the condenser 9 (step S24).
Here, the second and third switch elements 82 and 83 are
respectively changed to an opposite state. Thus, the second switch
82 is changed to an ON (close) state and the third switch element
83 is changed to an OFF (open) state (step S25). Then, CPU 4
compares the initially measured voltage V0 of the condenser 9 with
the primary power source voltage Vcc (step S26). If the initial
condenser voltage V0 does not reach to the primary power source
voltage Vcc (step S26, No), CPU 4 judges that the condenser 9 may
include some failures (step S30). On the other hand, if the initial
condenser voltage V0 exceeds the primary power source voltage Vcc
(step S26, Yes), CPU 4 compares the second measured voltage V1 of
the condenser 9 at the time T1 with a required minimum voltage Vt
at the same time T1 (step S27). If the second measured condenser
voltage V1 does not reach to the required minimum voltage Vt at the
time T1 (step S27, No), CPU 4 judges that the capacity of the
condenser 9 still falls short (step S29). Only when the second
measured condenser voltage V1 exceeds the required minimum voltage
Vt at the time T1 (step S27, Yes) does CPU 4 judge that the voltage
charged in the condenser is in a normal state (step S28). Thus CPU
4 judges that a sufficient voltage for performing power-off head
unloading operation has been charged in the condenser 9 as a
reserve power source.
FIG. 6 illustrates a permissible voltage curve for explaining how
to judge the normal/abnormal state of the condenser as the reserve
power source. In FIG. 6, an abscissa axis shows the time T and an
ordinate axis shows the voltage V charged in the condenser 9. If
the condenser 9 is a normal state, the allowable condenser voltage
curve Cn descends gradually from the primary power source battery
voltage Vcc at the time T0 as a function of time. On the contrary,
if the measured condenser voltage V0 at the time T0 does not reach
the primary power source voltage Vcc, as illustrated as the
measured condenser voltage curve Cm, it is judged as that the
voltage charged in the condenser 9 is not sufficient for performing
a head unloading operation. Even if the battery voltage Vcc has
been charged at the time T0, the voltage curve descends abruptly
with time, and at the time, T1, it may fall down lower than the
required minimum voltage Vt at the time T1. When the condenser 9
includes some failures, or damage, the measured condenser voltage
almost time independent since the voltage is not charged in the
condenser 9.
FIG. 7 illustrates another embodiment of the reserve power system
applicable to the magnetic disk drive apparatus, consistent with
the invention. In this embodiment, a reserve voltage power
necessary for performing the power-off head unloading operation is
supplied from both the condenser 9 and the back electromotive
voltage of the SPM 20.
As illustrated in FIG. 7, the SPM 20 includes three phase (U,V and
W) coils. The SPM driver 71 rotates the SPM 20 at a predetermined
speed by controlling current currents passing through each of the
coils of the SPM 20. With rotation of the three phase coils in the
SPM 20, it generates an induced alternate back electromotive
voltage. In order to obtain the reserve power by using the back
electromotive voltage, the reserve power system includes a
rectifying circuit 13 for rectifying the back electromotive voltage
and a power source stabilizing circuit 15 for stabilizing the
outputs of the rectifying circuit 13. The power source stabilizing
circuit 13 is comprised of a DC-DC converter.
A fourth switch unit 84 is provided between the output of the power
source stabilizing circuit 15 and the second power source line 92.
CPU 4 delivers a fourth control signal 840 for controlling ON/OFF
operations of the fourth switch unit 84. Further, a fifth switch
unit 85 is provided between the output of the rectifying circuit 13
and the power source stablizing circuit 15. CPU 4 delivers a fifth
control signal 850 for controlling ON/OF operations of the fifth
switch unit 85. Both the fourth and fifth switch units 84, 85 may
be comprised of a semiconductor, such as, for example, a FET. When
the primary power source for the apparatus is put on, CPU 4
supplies the first and fourth control signals 810 and 840 at a high
level for setting the first and fourth switch units 81 and 84 are
respectively closed. If a shutdown of the primary power source
occurs, the first and fourth switch units 81 and 84 are changed to
an ON (closed) state and the fifth switch unit 85 is opened in
accordance with the respective first, fourth and fifth switch
control signals 810, 840 and 850 supplied from CPU 4.
When a shutdown of the primary power source occurs, since the power
supply from the power source line 91 to the SPM driver 71 is cut
off, the output from the SPM driver 17 is disabled. However, the
SPM 20 still continues to rotate by an inertia force after the
output front the SPM driver 71 is disabled. Consequently, each coil
in the SPM 20 generates a back electromotive voltage for a while
after the shutdown of the power source.
The back electromotive voltages generated by all the coils of the
SPM 20 are rectified and converted to DC voltages by the rectifying
circuit 13. The fourth and fifth switch elements 84, 85 are closed
when the primary power source is shut down by the switch element
control signals 840, 850 of a low level. Then the DC voltage output
from the rectifying circuit 13 is converted to a stabilized DC
voltage through the power source stabilizing circuit 15. The
stabilized DC voltage is supplied only to the head unloading
control system including CPU 4 through the power source line 92.
Consequently, the head unloading control system including CPU 4 can
perform the head unloading control operation, even if the primary
power source for the apparatus has shut down.
In the embodiment illustrated in FIG. 7, in addition to the battery
voltage of the condenser 9, the back electromotive voltage of the
SPM 20 is also used as the reserve power source when a shutdown of
the primary power source occurs. Consequently, it becomes possible
for the condenser 9 to reduce its capacity. Thus, it may reduce a
manufacturing cost. By adding the battery voltage of the condenser
9 and the back electromotive voltage of the SPM 20, it may raise
the certainty of power off unloading operation.
In the above embodiments, the magnetic disk drive apparatus is
explained as a head loading/unloading apparatus. However, the
magnetic disk drive apparatus may also be the magnetic disk drive
apparatus of the CSS system wherein the head elements 12 are
retracted on the CSS area on the disk 10.
As explained above, prior to starting the head loading control, the
magnetic disk drive apparatus 100 and method for controlling head
unloading operation judges whether a sufficient electric power is
secured in a reserve system in order to retract the head elements
to a predetermined rest position if a shutdown of the power source
occurs. Thus, it becomes possible to perform certainly power off
unloading of head elements at the time of shutdown of the power
source.
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